Roses have been cultivated for thousands of years, admired for their beauty. Despite their use in fragrance, skincare and even in teas and jams, there are some things, however, that we still don’t know about these symbolic flowers.
And that includes the physical mechanism behind the shape of rose petals.
The curves and curls of leaves and flower petals arise due to the interplay between their natural growth and geometry.
Uneven growth in a flat sheet, in which the edges grow quicker than the interior, gives rise to strain and in plant leaves and petals, for example, this can result in a variety of shapes such as saddle and ripple shapes.
Yet when it comes to rose petals, the sharply pointed cusps – a point where two curves meet — that form at the edge of the petals set it apart from soft, wavy patterns seen in many other plants.
While young rose petals have smooth edges, as the rose matures the petals change to a polygonal shape with multiples cusps.
To investigate this intriguing difference, researchers from The Hebrew University of Jerusalem carried out theoretical modelling and conducted a series of experiments with synthetic disc “petals”.
They found that the pointed cusps that form at the edge of rose petals are due to a type of geometric frustration called a Mainardi-Codazzi-Peterson (MCP) incompatibility.
This type of mechanism results in stress concentrating in a specific area, which go on to form cusps to avoid tearing or forming unnatural folding.
When the researchers supressed the formation of cusps, they found that the discs reverted to being smooth and concave.
The researchers say that the findings could be used for applications in soft robotics and even the deployment of spacecraft components.
And it also goes some way to deepen our appreciation of nature’s ability to juggle growth and geometry.
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